Tapered sockets for aircraft engine mount assemblies

ABSTRACT

An engine mount assembly for coupling an engine to an airframe. The engine mount assembly includes a torsion bar coupled between the engine and the airframe. The torsion bar has upper and lower tapered bosses. Upper and lower arm assemblies couple the engine to the torsion bar. Each arm assembly has an end bell crank with a tapered socket that is adapted to receive a respective tapered boss therein to secure the end bell cranks to the torsion bar such that the end bell cranks rotate with the torsion bar responsive to movements of the engine.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. ProvisionalApplication No. 62/289,766, filed Feb. 1, 2016, the contents of whichare hereby incorporated by reference.

TECHNICAL FIELD OF THE DISCLOSURE

The present disclosure relates, in general, to engine mount assembliesfor use on aircraft and, in particular, to engine mount assemblies forcontrolling engine motion or vibration along various degrees of freedom.

BACKGROUND

An aircraft may have one or more engines that are secured within oragainst another portion of the aircraft, such as a nacelle or airframe.Due to their large size, power output and other characteristics,aircraft engines may move or vibrate during operation. Engine mounts, inaddition to securing engines on an aircraft, can be used to control orabsorb an engine's vibrations to prevent structural instability duringflight. Such instability may occur on rotorcraft, for example, if therotor and associated engine have conflicting modes of vibration. Furthercomplicating matters, engines may vibrate along multiple degrees offreedom at different respective magnitudes, including movement in thelateral, vertical and torsional directions. Load, motion, spatial andother operational constraints may require engine movement to be tuned orcontrolled in the vertical, lateral, and torsional directions. Currentengine mounts, however, fail to allow for an engine's movement along thevarious degrees of freedom to be independently controlled. For example,current engine mounts may have stiffness in the torsional direction andstiffness in the lateral direction that are coupled to one another suchthat changing the stiffness in the torsional direction affects thestiffness in the lateral direction, or vice versa, making lateral andtorsional engine movement difficult or impossible to independentlycontrol. Accordingly, a need has arisen for engine mounts that allowmotion or vibration along the various degrees of motion of an engine tobe independently tuned.

SUMMARY

In a first aspect, the present disclosure is directed to an engine mountassembly for coupling an engine to an airframe. The engine mountassembly includes a torsion bar coupled between the engine and theairframe. The torsion bar has an end including a tapered boss. An armassembly couples the end of the torsion bar to the engine. The armassembly includes an end bell crank having a tapered socket that isadapted to receive the tapered boss on the end of the torsion bar tosecure the end bell crank to the torsion bar such that the end bellcrank rotates with the torsion bar responsive to movements of theengine.

In some embodiments, the tapered boss may include a plurality of taperedsides to form a substantially polygonal boss and the tapered socket mayinclude a plurality of tapered sides to form a substantially polygonalsocket. In certain embodiments, the tapered boss may include first,second and third tapered sides to form a substantially triangular bossand the tapered socket may include first, second and third tapered sidesto form a substantially triangular socket. In some embodiments, each ofthe plurality of tapered sides of the tapered boss may have the sametaper angle and each of the plurality of tapered sides of the taperedsocket may have the same taper angle. In certain embodiments, theplurality of tapered sides of the tapered boss may have the same taperangle as the plurality of tapered sides of the tapered socket. In someembodiments, each of the plurality of tapered sides of the tapered bossmay be adapted to abut one of the tapered sides of the tapered socket.In certain embodiments, the engine mount assembly may include afastener, the tapered boss may include a receiving hole, the taperedsocket may include an aperture and the fastener may be insertable intothe aperture and the receiving hole to tighten the tapered socketagainst the tapered boss. In some embodiments, the receiving hole mayinclude a threaded receiving hole and the fastener may include a screwthreadable into the receiving hole.

In certain embodiments, the end bell crank may include a bell crank armforming a bell crank arm socket. In some embodiments, the arm assemblymay include a linkage having first and second ends, the bell crank armsocket adapted to receive the first end of the linkage. In certainembodiments, the bell crank arm may include at least one linkagesecuring aperture adjacent to the bell crank arm socket and the enginemount assembly may include a bolt insertable through the at least onelinkage securing aperture and the first end of the linkage to secure thefirst end of the linkage within the bell crank arm socket. In someembodiments, the engine mount assembly may include a spherical bearingwith the bell crank arm rotatably coupled to the first end of thelinkage via the spherical bearing. In certain embodiments, the enginemay be subject to lateral movement such that the torsion bar and the endbell crank may rotate in response to lateral movement of the engine. Insome embodiments, the engine may be subject to torsional movement suchthat the end bell crank may rotate in response to torsional movement ofthe torsion bar and the engine. In certain embodiments, the arm assemblymay include a scissor mount attachable to the engine and a linkagecoupling the scissor mount to the end bell crank.

In a second aspect, the present disclosure is directed to a rotorcraftincluding an airframe, an engine and an engine mount assembly adapted tomount the engine to the airframe. The engine mount assembly includes atorsion bar having an end including a tapered boss and an arm assemblycoupling the end of the torsion bar to the engine. The arm assemblyincludes an end bell crank having a tapered socket that is adapted toreceive the tapered boss on the end of the torsion bar to secure the endbell crank to the torsion bar such that the end bell crank rotates withthe torsion bar responsive to movements of the engine.

In a third aspect, the present disclosure is directed to a tiltrotoraircraft having a helicopter mode and an airplane mode. The tiltrotoraircraft includes an airframe including a fuselage, a wing and anacelle. An engine is disposed within the nacelle. An engine mountassembly is adapted to mount the engine to the airframe. The enginemount assembly includes a torsion bar having an end including a taperedboss and an arm assembly coupling the end of the torsion bar to theengine. The arm assembly includes an end bell crank having a taperedsocket that is adapted to receive the tapered boss on the end of thetorsion bar to secure the end bell crank to the torsion bar such thatthe end bell crank rotates with the torsion bar responsive to movementsof the engine.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the features and advantages of thepresent disclosure, reference is now made to the detailed descriptionalong with the accompanying figures in which corresponding numerals inthe different figures refer to corresponding parts and in which:

FIGS. 1A-1B are schematic illustrations of a tiltrotor aircraftutilizing engine mount assemblies in accordance with embodiments of thepresent disclosure;

FIG. 2A is an isometric view of an exemplary propulsion system for atiltrotor aircraft utilizing an engine mount assembly in accordance withembodiments of the present disclosure;

FIG. 2B is a top view of an exemplary wing section of a tiltrotoraircraft that includes an engine mount assembly in accordance withembodiments of the present disclosure;

FIG. 3A is an isometric view of a fixed pylon in which an engine ismounted using an engine mount assembly in accordance with embodiments ofthe present disclosure;

FIGS. 3B-3D are various views of an engine mount assembly in accordancewith embodiments of the present disclosure;

FIGS. 4A-4D and 5A-5D are various views of an engine mount assemblyresponding to lateral movement of an engine in accordance withembodiments of the present disclosure;

FIGS. 6A-6D and 7A-7D are various views of an engine mount assemblyresponding to torsional movement of an engine in accordance withembodiments of the present disclosure;

FIGS. 8A-8B are front views of an engine mount assembly responding tovertical movement of an engine in accordance with embodiments of thepresent disclosure;

FIGS. 9 and 10A-10D are various views of an end bell crank of an enginemount assembly in accordance with embodiments of the present disclosure;

FIG. 11 is a front view of a lateral movement control assembly of anengine mount assembly in accordance with embodiments of the presentdisclosure;

FIGS. 12A-12D are various views of a middle bell crank of an enginemount assembly in accordance with embodiments of the present disclosure;

FIGS. 13A-13B are various views of a beam spring of an engine mountassembly in accordance with embodiments of the present disclosure;

FIGS. 14-16 and 17A-17B are various views of a sleeved bolt assembly ofan engine mount assembly in accordance with embodiments of the presentdisclosure; and

FIG. 18 is a cross-sectional view of a traditional bolt assembly.

DETAILED DESCRIPTION

While the making and using of various embodiments of the presentdisclosure are discussed in detail below, it should be appreciated thatthe present disclosure provides many applicable inventive concepts,which can be embodied in a wide variety of specific contexts. Thespecific embodiments discussed herein are merely illustrative and do notdelimit the scope of the present disclosure. In the interest of clarity,all features of an actual implementation may not be described in thisspecification. It will of course be appreciated that in the developmentof any such actual embodiment, numerous implementation-specificdecisions must be made to achieve the developer's specific goals, suchas compliance with system-related and business-related constraints,which will vary from one implementation to another. Moreover, it will beappreciated that such a development effort might be complex andtime-consuming but would nevertheless be a routine undertaking for thoseof ordinary skill in the art having the benefit of this disclosure.

In the specification, reference may be made to the spatial relationshipsbetween various components and to the spatial orientation of variousaspects of components as the devices are depicted in the attacheddrawings. However, as will be recognized by those skilled in the artafter a complete reading of the present disclosure, the devices,members, apparatuses, and the like described herein may be positioned inany desired orientation. Thus, the use of terms such as “above,”“below,” “upper,” “lower” or other like terms to describe a spatialrelationship between various components or to describe the spatialorientation of aspects of such components should be understood todescribe a relative relationship between the components or a spatialorientation of aspects of such components, respectively, as the devicesdescribed herein may be oriented in any desired direction.

Referring to FIGS. 1A-1B and 2A-2B in the drawings, a tiltrotor aircraftis schematically illustrated and generally designated 10. Aircraft 10includes a fuselage 12, a wing mount assembly 14 and a tail assembly 16including rotatably mounted tail members 16 a, 16 b having controlsurfaces operable for horizontal and/or vertical stabilization duringforward flight. A wing member 18 is supported by wing mount assembly 14.Located at outboard ends of wing member 18 are propulsion assemblies 20a, 20 b. Propulsion assembly 20 a includes a nacelle depicted as fixedpylon 22 a that houses an engine 24 and a transmission 26. Thus, thenacelle is fixed relative to wing member 18. In addition, propulsionassembly 20 a includes a mast assembly 28 a that is rotatable relativeto fixed pylon 22 a between a generally horizontal orientation, as bestseen in FIG. 1A, and a generally vertical orientation, as best seen inFIG. 1B. Propulsion assembly 20 a also includes a proprotor assembly 30a that is rotatable relative to mast assembly 28 a responsive to torqueand rotational energy provided via a rotor hub assembly and drive systemmechanically coupled to engine 24 and transmission 26. Similarly,propulsion assembly 20 b includes a nacelle depicted as fixed pylon 22 bthat houses an engine and transmission, a mast assembly 28 b that isrotatable relative to fixed pylon 22 b and a proprotor assembly 30 bthat is rotatable relative to mast assembly 28 b responsive to torqueand rotational energy provided via a rotor hub assembly and drive systemmechanically coupled to the engine and transmission housed by fixedpylon 22 b. As used herein, including in the claims, the term “coupled”may include direct or indirect coupling by any means, including movingand/or non-moving mechanical connections.

FIG. 1A illustrates aircraft 10 in airplane or forward flight mode, inwhich proprotor assemblies 30 a, 30 b are rotating in a substantiallyvertical plane to provide a forward thrust enabling wing member 18 toprovide a lifting force responsive to forward airspeed, such thataircraft 10 flies much like a conventional propeller driven aircraft.Unless otherwise indicated, as used herein, “or” does not require mutualexclusivity. FIG. 1B illustrates aircraft 10 in helicopter or verticaltakeoff and landing (VTOL) flight mode, in which proprotor assemblies 30a, 30 b are rotating in a substantially horizontal plane to provide alifting thrust, such that aircraft 10 flies much like a conventionalhelicopter. It should be appreciated that aircraft 10 can be operatedsuch that proprotor assemblies 30 a, 30 b are selectively positionedbetween forward flight mode and VTOL flight mode, which can be referredto as a conversion flight mode. Even though aircraft 10 has beendescribed as having one engine in each fixed pylon 22 a, 22 b, it shouldbe understood by those having ordinary skill in the art that otherengine arrangements are possible and are considered to be within thescope of the present disclosure including, for example, having a singleengine which may be housed within fuselage 12 that provides torque androtational energy to both proprotor assemblies 30 a, 30 b.

Engine 24 is mounted within fixed pylon 22 a by engine mount assembly32. Engine mount assembly 32 may be mounted onto an aft portion ofengine 24, as illustrated. Engine 24 is subject to movement, includingvibration, in multiple directions, or degrees of freedom, including thelateral, vertical and torsional directions. When engine 24 vibrates atparticular frequencies, structural instability of fixed pylon 22 a oranother portion of aircraft 10 can result. For example, structuralinstability can result if engine 24 vibrates at an excitation frequencyoriginating from proprotor assembly 30 a. Engine mount assembly 32controls movement, including vibration frequencies, of engine 24 bytailoring the stiffness of various constituent structures or componentsto counteract the movement of engine 24 in the lateral, vertical andtorsional directions. Furthermore, engine mount assembly 32 is capableof independently controlling the movement of engine 24 in any onedirection, while not affecting the movement of engine 24 in any otherdirection, thereby decoupling control of the lateral, vertical andtorsional movement of engine 24 from each other. For example, enginemount assembly 32 is capable of increasing the stiffness working againstthe lateral movement of engine 24 without affecting the stiffnessworking against the torsional movement of engine 24, or vice versa. Suchindependent control allows engine mount assembly 32 to, for example,more easily meet operational vibration ranges or targets of engine 24 ineach of the lateral, vertical and torsional directions. Engine mountassembly 32 provides the capability of controlling stiffness in thelateral, vertical and torsional load directions to tailor dynamic tuningof engine 24, and thus achieve reductions in oscillatory loading andvibration.

Referring now to FIGS. 2A-2B, propulsion assembly 20 a is disclosed infurther detail. Propulsion assembly 20 a is substantially similar topropulsion assembly 20 b therefore, for sake of efficiency, certainfeatures will be disclosed only with regard to propulsion assembly 20 a.One having ordinary skill in the art, however, will fully appreciate anunderstanding of propulsion assembly 20 b based upon the disclosureherein of propulsion assembly 20 a. Engine 24 of propulsion assembly 20a is substantially fixed relative to wing 18, although some motion ofengine 24 occurs during operation. In particular, engine mount assembly32 allows for the controlled motion of engine 24. An engine output shaft34 transfers power from engine 24 to a spiral bevel gearbox 36 thatincludes spiral bevel gears to change torque direction by 90 degreesfrom engine 24 to a fixed gearbox 38 via a clutch. Fixed gearbox 38includes a plurality of gears, such as helical gears, in a gear trainthat are coupled to an interconnect drive shaft 40 and a quill shaft(not visible) that supplies torque to an input in spindle gearbox 42 ofproprotor gearbox 44. Interconnect drive shaft 40 provides a torque paththat enables a single engine of aircraft 10 to provide torque to bothproprotor assemblies 30 a, 30 b in the event of a failure of the otherengine. In the illustrated embodiment, interconnect drive shaft 40includes a plurality of segments that share a common rotational axis.

Engine 24 is housed and supported in fixed pylon 22 a (see FIGS. 1A-1B)that may include features such as an inlet, aerodynamic fairings andexhaust, as well as other structures and systems to support andfacilitate the operation of engine 24. The airframe of aircraft 10,which supports the various sections of aircraft 10 including fuselage12, includes a propulsion assembly airframe section 46 that supportspropulsion assembly 20 a. Engine mount assembly 32 is coupled topropulsion assembly airframe section 46 to support engine 24. Proprotorassembly 30 a of propulsion assembly 20 a includes three rotor blades 48a, 48 b, 48 c that are coupled to a rotor hub 50. Rotor hub 50 iscoupled to a mast 52 that is coupled to proprotor gearbox 44. Together,spindle gearbox 42, proprotor gearbox 44 and mast 52 are part of mastassembly 28 a that rotates relative to fixed pylon 22 a. In addition, itshould be appreciated by those having ordinary skill in the art thatmast assembly 28 a may include different or additional components, suchas a pitch control assembly depicted as swashplate 54, actuators 56 andpitch links 58, wherein swashplate 54 is selectively actuated byactuators 56 to selectively control the collective pitch and the cyclicpitch of rotor blades 48 a, 48 b, 48 c via pitch links 58. A linearactuator, depicted as conversion actuator 60 of fixed pylon 22 a, isoperable to reversibly rotate mast assembly 28 a relative to fixed pylon22 a, which in turn selectively positions proprotor assembly 30 abetween forward flight mode, in which proprotor assembly 30 a isrotating in a substantially vertical plane, and VTOL flight mode, inwhich proprotor assembly 30 a is rotating in a substantially horizontalplane.

It should be appreciated that aircraft 10 is merely illustrative of avariety of aircraft that can implement the embodiments disclosed herein.Indeed, engine mount assembly 32 may be utilized on any aircraft havingone or more engines. Other aircraft implementations can include hybridaircraft, tiltwing aircraft, quad tiltrotor aircraft, unmanned aircraft,gyrocopters, airplanes, jets, helicopters and the like. As such, thoseof ordinary skill in the art will recognize that engine mount assembly32 can be integrated into a variety of aircraft configurations. Itshould be appreciated that even though aircraft are particularlywell-suited to implement the embodiments of the present disclosure,non-aircraft vehicles and devices can also implement the embodiments,including, but not limited to, automobiles or land-based vehicles.

Referring to FIGS. 3A-3D, 4A-4D, 5A-5D, 6A-6D, 7A-7D and 8A-8B in thedrawings, a propulsion assembly including an engine mount assembly isgenerally designated 100. Propulsion assembly 100 includes airframe 102.The illustrated portion of airframe 102 is a section of the airframe forthe aircraft that supports propulsion assembly 100. Engine mountassembly 104 mounts engine 106 to airframe 102. In the illustratedembodiment, engine mount assembly 104 attaches to aft portion 108 ofengine 106, although engine mount assembly 104, in other embodiments,may attach to any portion of engine 106. Engine 106 is subject tolateral movement, as shown in FIGS. 4A-4D and 5A-5D, torsional movement,as shown in FIGS. 6A-6D and 7A-7D, and vertical movement, as shown inFIGS. 8A-8B. Lateral, torsional and vertical movement includes, but isnot limited to, lateral, torsional and vertical vibration, modes ofvibration or other oscillatory motion, respectively. Engine mountassembly 104 is capable of independently tailoring stiffness along thelateral, torsional and vertical load paths of engine 106 to allow forindependent control of the lateral, torsional and vertical movement ofengine 106.

Engine mount assembly 104 includes a support spine 110 coupled toairframe 102. A torsion bar 112 is vertically mounted within propulsionassembly 100, and is rotatably coupled to support spine 110 by upper andlower torsion bar bearing mounts 114 a, 114 b. Upper and lower torsionbar bearing mounts 114 a, 114 b are rotatably coupled to upper and lowerportions 116 a, 116 b of torsion bar 112, respectively, to permit axialrotation of torsion bar 112 about its longitudinal axis. The interfacebetween torsion bar 112 and upper and lower torsion bar bearing mounts114 a, 114 b may include bearings to facilitate the rotation of torsionbar 112. Upper and lower torsion bar bearing mounts 114 a, 114 b arefixedly coupled to support spine 110.

Torsion bar 112 is coupled to engine 106. When torsion bar 112experiences torsion, torsion bar 112 has a torsional stiffness that iscapable of independently controlling torsional movement of engine 106.Top and bottom ends 118 a, 118 b of torsion bar 112 are coupled to topand bottom sides 120 a, 120 b of engine 106 by top and bottom armassemblies 122 a, 122 b, respectively. Top arm assembly 122 a includestop end bell crank 124 a fixedly coupled to top end 118 a of torsion bar112, a top scissor mount 126 a coupled to top engine lugs 128 a, 128 bon top side 120 a of engine 106 and a top linkage 130 a coupling top endbell crank 124 a to top scissor mount 126 a. Bottom arm assembly 122 bincludes bottom end bell crank 124 b fixedly coupled to bottom end 118 bof torsion bar 112, bottom scissor mount 126 b coupled to bottom enginelugs 128 c, 128 d on bottom side 120 b of engine 106 and bottom linkage130 b coupling bottom end bell crank 124 b to bottom scissor mount 126b. Loads caused by lateral and torsional movement of engine 106 aretransferred to torsion bar 112 via top and bottom arm assemblies 122 a,122 b.

Top scissor mount 126 a includes blades 132 a, 132 b rotatably coupledto one another at a fulcrum 134 a. Blades 132 a, 132 b are eachbifurcated into tines 136 between which top engine lugs 128 a, 128 b maybe interposed. Bottom scissor mount 126 b includes blades 132 c, 132 drotatably coupled to one another at fulcrum 134 b. Blades 132 c, 132 deach bifurcate into tines 138 between which bottom engine lugs 128 c,128 d may be interposed. The rotatable connection between blades 132 a,132 b at fulcrum 134 a for top scissor mount 126 a and between blades132 c, 132 d at fulcrum 134 b for bottom scissor mount 126 b preventsstresses and loads on engine 106 by allowing scissor mounts 126 a, 126 bto open and close in response to, for example, thermal expansion ofengine 106. Any bolt, pin or other fastener may be used at fulcrums 134a, 134 b that allows for blades 132 a, 132 b and blades 132 c, 132 d torotate relative to one another, respectively. Ends 140 a, 140 b of toplinkage 130 a may be movably coupled to top scissor mount 126 a and topend bell crank 124 a via spherical bearings. Likewise, ends 140 c, 140 dof bottom linkage 130 b may be movably coupled to bottom scissor mount126 b and bottom end bell crank 124 b via spherical bearings. Thespherical bearings located at ends 140 a, 140 b, 140 c, 140 d oflinkages 130 a, 130 b allow top and bottom arm assemblies 122 a, 122 bto accommodate vertical and fore-aft movement of engine 106. Forexample, when engine 106 moves vertically, as shown in FIGS. 8A-8B, thespherical bearings allow linkages 130 a, 130 b to rotate up and downrelative to end bell cranks 124 a, 124 b, respectively, so that verticalmotion may be accommodated by top and bottom arm assemblies 122 a, 122b.

Engine mount assembly 104 includes a lateral movement control assembly142 coupled to torsion bar 112. Lateral movement control assembly 142,or a portion thereof, has a lateral stiffness that controls lateralmovement of engine 106. Lateral movement control assembly 142 includes amiddle bell crank 144 fixedly coupled to a middle section 146 of torsionbar 112. Middle bell crank 144 may be fixedly coupled at the midpoint oftorsion bar 112, or, as illustrated, may be slightly offset from themidpoint of torsion bar 112. For example, for a torsion bar measuringapproximately 18 inches in length, middle bell crank 144 may be offsetfrom the midpoint of torsion bar 112 by 3 inches or less. In thisexample, middle bell crank 144 may be offset from the midpoint oftorsion bar 112 by 1-2 inches. Middle bell crank 144 is coupled to aspring 148 by a lateral link 150. In some embodiments, middle bell crank144 may be coupled to lateral link 150 via a spherical bearing, therebyallowing for a range of motion between middle bell crank 144 and laterallink 150 in multiple degrees of freedom. When engine 106 moveslaterally, torsion bar 112 rotates and middle bell crank 144 transfersthe rotational energy of torsion bar 112 to spring 148. Spring 148 has alateral stiffness that controls or restrains lateral movement of engine106. Spring 148 may be any type of spring, such as a coiled spring, leafspring or flexure, and may be made of any material such as elastomer,silicone, composite or metal. Indeed, spring 148 may be any shape, andbe made from any material, capable of being compressed or stretched toprovide a suitable stiffness or elasticity to control the lateralmovement of engine 106. In other embodiments, more than one spring maybe utilized to obtain a lateral stiffness for the lateral movementcontrol assembly 142.

Engine mount assembly 104 includes a vertical movement control assembly152 that has a vertical stiffness to independently control the verticalmovement of engine 106. Vertical movement control assembly 152 isdivided into a top vertical movement control assembly 154 a coupled totop side 120 a of engine 106 via top scissor mount 126 a and bottomvertical movement control assembly 154 b coupled to bottom side 120 b ofengine 106 via bottom scissor mount 126 b. Top vertical movement controlassembly 154 a includes a top support arm 156 a fixedly coupled toairframe 102. Top support arm 156 a is coupled to top scissor mount 126a by a top vertical support linkage 158 a. Top end 160 a of top verticalsupport linkage 158 a is coupled to top support arm 156 a and bottom end160 b of top vertical support linkage 158 a is coupled to fulcrum 134 aof top scissor mount 126 a. In some embodiments, top end 160 a of topvertical support linkage 158 a is movably coupled to top support arm 156a via a spherical bearing and bottom end 160 b of top vertical supportlinkage 158 a is movably coupled to fulcrum 134 a of top scissor mount126 a via a spherical bearing to permit engine 106 to move in multipledegrees of freedom, including the fore-aft direction.

Bottom vertical movement control assembly 154 b includes bottom supportarm 156 b fixedly coupled to support spine 110. In other embodiments,bottom support arm 156 b may be directly coupled to airframe 102. In yetother embodiments, support spine 110 and bottom support arm 156 b may bea single part formed from the same piece of material. Bottom verticalmovement control assembly 154 b includes bottom vertical support linkage158 b coupling bottom support arm 156 b to bottom side 120 b of engine106 via bottom scissor mount 126 b. Top end 160 c of bottom verticalsupport linkage 158 b is coupled to fulcrum 134 b of bottom scissormount 126 b and bottom end 160 d of bottom vertical support linkage 158b is coupled to bottom support arm 156 b. In some embodiments, ends 160c, 160 d of bottom vertical support linkage 158 b may each be coupled tofulcrum 134 b and bottom support arm 156 b, respectively, via sphericalbearings to permit engine 106 to move in multiple degrees of freedom,including the fore-aft direction. Top vertical support linkage 158 a hasa loop structure and bottom vertical support linkage 158 b has a linearstructure. In other embodiments, however, either or both of top orbottom vertical support linkages 158 a, 158 b may have a looped, linearor any other structure suitable for the application. Both the top andbottom vertical movement control assemblies 154 a, 154 b have verticalstiffnesses that may be selected to control vertical movement of engine106.

Referring specifically to FIGS. 4A-4D, 5A-5D, 6A-6D, 7A-7D and 8A-8B,engine mount assembly 104 operates to provide different load paths forlateral, torsional and vertical movement of engine 106 so that thestiffnesses in each of these directions are decoupled, or independentlycontrolled, from one another. In particular, lateral movement of engine106, as illustrated in FIGS. 4A-4D and 5A-5D is independentlycontrollable based on the lateral stiffness of spring 148. Torsionalmovement of engine 106, as shown in FIGS. 6A-6D and 7A-7D, isindependently controllable based on the torsional stiffness of torsionbar 112. The vertical movement of engine 106, as shown in FIGS. 8A-8B,is independently controllable based on the vertical stiffnesses of topand bottom vertical movement control assemblies 154 a, 154 b. Becausethe lateral, torsional and vertical load paths are stiffened bydifferent elements of engine mount assembly 104, movement, includingvibration, of engine 106 in the lateral, torsional and verticaldirections may be controlled independently of one another to allow forthe fine tuning of stiffnesses in each of these directions to meetoperational parameters or constraints.

Referring specifically to FIGS. 4A-4D and 5A-5D, the lateral load pathof engine mount assembly 104 is illustrated. When engine 106 is at restand experiences no movement or vibration, engine 106 is in a neutralposition 162. When engine 106 moves to an outer lateral position 164, asshown in FIG. 4A, such movement is transferred through top and bottomarm assemblies 122 a, 122 b to rotate end bell cranks 124 a, 124 b inthe same direction that engine 106 has moved. End bell cranks 124 a, 124b rotate in the same direction away from support spine 110 as best seenin FIGS. 4B and 4D. Because end bell cranks 124 a, 124 b are fixedlycoupled to ends 118 a, 118 b of torsion bar 112, respectively, torsionbar 112 rotates in the same direction as end bell cranks 124 a, 124 b.Middle bell crank 144, by virtue of being fixedly coupled to middlesection 146 of torsion bar 112, rotates in the same direction as endbell cranks 124 a, 124 b and torsion bar 112, thus transferring therotational energy of torsion bar 112 to spring 148. The rotation ofmiddle bell crank 144 in the same direction as end bell cranks 124 a,124 b is best seen in FIG. 4C. Conversely, when engine 106 moves to aninner lateral position 166, as shown in FIG. 5A, end bell cranks 124 a,124 b and middle bell crank 144 all rotate in the same direction ofmovement of engine 106 and toward support spine 110, as shown in FIGS.5B-5D. Thus, the lateral load path of engine mount assembly 104 isdirected to spring 148, whose lateral stiffness controls the lateralmovement of engine 106. A suitable lateral stiffness of spring 148 maybe obtained by varying the shape of spring 148 or the material fromwhich spring 148 is composed. In this manner, lateral movement of engine106 is controlled independently from torsional and vertical movement ofengine 106. Thus, changing the lateral stiffness of spring 148 does notsubstantially affect the torsional and vertical movement of engine 106.

Referring specifically to FIGS. 6A-6D and 7A-7D, the torsional load pathof engine mount assembly 104 is illustrated. Engine 106 oscillates aboutengine axis 168 from neutral position 162, in which engine 106 issubstantially vertical. In FIG. 6A, top side 120 a of engine 106 hastilted away from torsion bar 112 while bottom side 120 b of engine 106has tilted toward torsion bar 112, thus causing end bell cranks 124 a,124 b to rotate in opposite directions, as shown in FIGS. 6B and 6D. Endbell cranks 124 a, 124 b also move in opposite directions when top side120 a of engine 106 tilts toward torsion bar 112 and bottom side 120 bof engine 106 tilts away from torsion bar 112, as shown in FIGS. 7A-7D.When torsional movement of engine 106 causes end bell cranks 124 a, 124b to rotate in opposite directions, torsion bar 112 experiences torsion.Thus, the torsional stiffness of torsion bar 112 controls the torsionalmovement of engine 106. In some embodiments, torsional stiffness oftorsion bar 112 may be expressed as GJ/L, wherein G is the rigiditymodulus of the material from which torsion bar 112 is made, J is thetorsion constant for torsion bar 112 and L is the length of torsion bar112.

The torsional stiffness of torsion bar 112 may be varied to achieve adesired amount of torsional movement for engine 106. For example, thediameter of torsion bar 112 may be increased to decrease the torsionalmovement of engine 106. Conversely, the diameter of torsion bar 112 maybe decreased to allow additional torsional movement for engine 106.Also, while torsion bar 112 is illustrated as having a generallycylindrical shape, torsion bar 112 may have a cross-sectional shapeother than a circle, such as a square, polygon or other shape. The shapeof torsion bar 112 may be varied to change the torsional stiffness oftorsion bar 112. The torsional stiffness of torsion bar 112 may also bevaried by changing the material from which torsion bar 112 is made. Insome embodiments, torsion bar 112 may be a metal or composite tube orrod. For example, torsion bar 112 may be formed from steel, such asstainless steel. Torsion bar 112 may also be any length depending on theapplication, and may be affected by the size of engine 106 or enginemount assembly 104, as well as other factors.

The torsional load path of engine mount assembly 104 is directed totorsion bar 112 such that torsional movement of engine 106 is controlledby the torsional stiffness of torsion bar 112. Torsion bar 112 transmitsthe lateral motion of engine 106 to spring 148, but self-reacts totorsional movement of engine 106. Middle bell crank 144, by virtue ofbeing located in middle section 146 of torsion bar 112, is substantiallystationary when engine 106 experiences torsional movement, as shown inFIGS. 6C and 7C, and thus does not exert a force upon spring 148. Thus,torsional movement of engine 106 is controlled independently of lateralmovement of engine 106. The torsional stiffness of torsion bar 112,while controlling torsional movement of engine 106, does notsubstantially affect lateral and vertical movement of engine 106. Thus,torsion bar 112 can be designed or selected so as to achieve desiredtuning in the torsional load direction.

Referring to FIGS. 8A and 8B, the vertical load path of engine mountassembly 104 is illustrated. In FIG. 8A, engine 106 has moved downwardfrom neutral position 162, thereby stretching top vertical movementcontrol assembly 154 a and compressing bottom vertical movement controlassembly 154 b. In FIG. 8B, engine 106 has moved upward of neutralposition 162, thereby compressing top vertical movement control assembly154 a and stretching bottom vertical movement control assembly 154 b.The vertical stiffnesses of top and bottom vertical movement controlassemblies 154 a, 154 b, including support arms 156 a, 156 b andvertical support linkages 158 a, 158 b, control vertical movement ofengine 106 independent of lateral or torsional movement of engine 106.Utilizing stiffer materials or shapes for support arms 156 a, 156 b andvertical support linkages 158 a, 158 b limits vertical movement ofengine 106, while more elastic materials or shapes for support arms 156a, 156 b or vertical support linkages 158 a, 158 b permits more verticalmovement of engine 106. Vertical support linkages 158 a, 158 b may bemade from elastomer, silicone, composite, metal or other suitablematerials. In some embodiments, support arms 156 a, 156 b or verticalsupport linkages 158 a, 158 b may be made from titanium or steel, suchas stainless steel. Vertical support linkages 158 a, 158 b may also bemetal flexures. Because vertical motion of engine 106 is controlled bythe stiffness of vertical movement control assemblies 154 a, 154 b,while torsional motion of engine 106 is controlled by the torsionalstiffness of torsion bar 112 and lateral motion of engine 106 iscontrolled by the lateral stiffness of spring 148, vertical motion ofengine 106 is controlled independently of both lateral and verticalmovement of engine 106.

Thus, the lateral, torsional and vertical load paths are each directedto different elements of engine mount assembly 104, namely spring 148,torsion bar 112 and vertical movement control assembly 152, thusallowing individual stiffness tailoring of the lateral, torsional andvertical load paths. The stiffness of the lateral load path can betailored by design of spring 148, the stiffness of the torsional loadpath can be tailored by design of torsion bar 112, and the stiffness ofthe vertical load path can be tailored by design of the verticalmovement control assembly 152. By using the illustrative embodiments,placement of the engine's natural frequencies may be tailored to theparticular application. Individual stiffness targets or ranges in thelateral, torsional or vertical directions may be more easily met sincethe adjustment of stiffness in any one of these directions does notaffect the other two. In effect, stiffness in any one of the lateral,torsional or vertical directions can be isolated or decoupled from thestiffness in the other two directions. In contrast, previous enginemounting configurations cannot independently tune each of thefundamental lateral, torsional and vertical engine modes of vibration.For example, stiffening one load path in these previous systems toincrease a desired engine mode would subsequently increase the modeplacement of the other coupled direction, thus making stiffnesstailoring for dynamic tuning difficult or even impossible to achieve. Itwill be appreciated by one of ordinary skill in the art that lateral,torsional and vertical movement of engine 106 encompasses lateral,torsional and vertical modes of vibration of engine 106 such that themodes of vibration in each of these directions may be independentlycontrolled by the illustrative embodiments. Thus, undesirable modes ofvibration in any of these directions may be eliminated using theillustrative embodiments. By way of non-limiting example, the frequencyof oscillation of engine 106 in any of the lateral, torsional orvertical directions may be kept in a range of 12-14 Hz to eliminateinterference with a vibrational mode from another structure of theaircraft.

Referring to FIGS. 9 and 10A-10D, an engine mount assembly havingtapered socket connections is generally designated 200. Engine mountassembly 200 includes top and bottom end bell cranks 202, 204 fixedlycoupled to top and bottom ends 206, 208 of torsion bar 210,respectively. End bell cranks 202, 204 rotate in the same direction inresponse to lateral movement of the engine, and rotate in oppositedirections in response to torsional movement of the engine. End bellcranks 202, 204 are both fixedly coupled to torsion bar 210 using atapered socket connection, which is representatively described withreference to top end bell crank 202 in FIGS. 10A-10D. Top end 206 oftorsion bar 210 includes a tapered boss 212. Top end bell crank 202forms a tapered socket 214. Tapered socket 214 receives tapered boss 212to secure top end bell crank 202 to torsion bar 210 such that top endbell crank 202 rotates with torsion bar 210.

Tapered boss 212 has three tapered sides 216 to form a substantiallytriangular boss. Tapered boss 212, however, may have any number oftapered sides to form any polygonal shape. Tapered socket 214 also hasthree tapered sides 218 to form a substantially triangular socket toconformably receive tapered boss 212. In other embodiments, however,tapered socket 214 may have any number of tapered sides to form anypolygonal shape. Tapered boss 212 or tapered socket 214 may have eithera symmetric or non-symmetric shape. In other embodiments, tapered boss212 and tapered socket 214 may form external and internal splines toform a splined connection. In yet other embodiments, a screw drive maybe utilized to connect top end bell crank 202 to top end 206 of torsionbar 210. Tapered sides 216 of tapered boss 212 each have the same taperangle 220. Likewise, tapered sides 218 of tapered socket 214 each havethe same taper angle 222. Taper angle 220 of tapered sides 216 oftapered boss 212 is substantially the same as taper angle 222 of taperedsides 218 of tapered socket 214. When tapered socket 214 receivestapered boss 212, tapered sides 216 of tapered boss 212 each abut atleast a portion of one of tapered sides 218 of tapered socket 214 toprovide a firm and secure contact connection between top end bell crank202 and top end 206 of torsion bar 210. Taper angles 220, 222 may be anyangle that provides a firm, secure or fixed connection, including, butnot limited to, 1 degree, 5 degrees, 10 degrees or any other suitableangle.

The connection between top end bell crank 202 and torsion bar 210 may befurther secured by a screw 224 or other fastener. Tapered boss 212includes a threaded receiving hole 226. Tapered socket 214 forms anaperture 228. Screw 224 is inserted through aperture 228 and threadedreceiving hole 226 to tighten tapered socket 214 against tapered boss212, thereby pressing tapered sides 218 of tapered socket 214 againsttapered sides 216 of tapered boss 212. The force exerted by screw 224reduces movement between tapered socket 214 and tapered boss 212. Awasher 230 may be used to further secure the connection. In otherembodiments, threaded receiving hole 226 may be non-threaded orstraight, and screw 224 may be a non-threaded fastener, such as a boltor pin. By driving the female taper of tapered socket 214 onto the maletaper of tapered boss 212, backlash or “slop” between torsion bar 210and top end bell crank 202 may be reduced or eliminated. Tapered boss212 and tapered socket 214 of top end bell crank 202 is representativeof the tapered boss and tapered socket that may be used to fixedlycouple bottom end bell crank 204 to bottom end 208 of torsion bar 210.In addition, the tapered sockets and bosses of the illustrativeembodiments may be used to secure connections elsewhere on engine mountassembly 200.

Top end bell crank 202 includes a bell crank arm 232 that forms a bellcrank arm socket 234. Bell crank arm socket 234 is adapted to receiveend 236 of linkage 238. Bell crank arm 232 includes linkage securingapertures 240, 242 adjacent to bell crank arm socket 234. A bolt 244 isinsertable through linkage securing apertures 240, 242 and end 236 oflinkage 238 to secure end 236 of linkage 238 within bell crank armsocket 234. In some embodiments, end 236 of linkage 238 may be movablycoupled to bell crank arm 232 at bell crank arm socket 234 via aspherical bearing. The same or similar features described for top endbell crank 202 may also be included for bottom end bell crank 204,including the connection between linkage 246 and bottom end bell crank204.

Referring to FIGS. 11, 12A-12D and 13A-13B in the drawings, a lateralmovement control assembly for an engine mount assembly is schematicallyillustrated and generally designated 300. In response to lateralmovement of the engine, torsion bar 302 rotates, which causes middlebell crank 304 to rotate in the same direction as torsion bar 302 suchthat the rotational energy of torsion bar 302 is transferred to a beamspring 306 via interposed lateral link 308. The lateral stiffness ofbeam spring 306 controls lateral movement of the engine. The position ofmiddle bell crank 304 near midpoint 310 of torsion bar 302 causes middlebell crank 304 to remain substantially stationary when torsion bar 302experiences torsion in response to torsional movement of the engine. Insome embodiments, middle bell crank 304 may be slightly offset frommidpoint 310 of torsion bar 302. For example, for a torsion barmeasuring approximately 18 inches in length, middle bell crank 304 maybe offset from midpoint 310 by 1-2 inches to accommodate spatialconsiderations around the engine. In order for middle bell crank 304 toeffectively rotate with torsion bar 302, without the adverse effects ofbacklash or “slop,” the illustrated embodiment utilizes a spline tofixedly couple middle bell crank 304 to torsion bar 302. Lateralmovement control assembly 300 is coupled to middle section 312 oftorsion bar 302. Middle section 312 of torsion bar 302 includes anexternal spline 314. In a non-limiting example, for a torsion barmeasuring approximately 18 inches in length, external spline 314 may beoffset from midpoint 310 by 3 inches or less. In other embodiments,middle section 312 of torsion bar 302 may have a reduced diameteradjacent to external spline 314, as shown in FIG. 12D. In suchembodiments, middle section 312, or a portion thereof, may be machinedto a smaller diameter to accommodate external spline 314.

Middle bell crank 304 includes a clamp 316 that forms an internal spline318 that mates with external spline 314 of torsion bar 302 to securemiddle bell crank 304 to torsion bar 302 such that middle bell crank 304rotates with torsion bar 302. Clamp 316 includes two branches 320, 322each forming a portion of internal spline 318. Branches 320, 322 eachinclude a securing tab 324, 326. Securing tabs 324, 326 are pressabletoward one another to secure clamp 316 to torsion bar 302. Securing tabs324, 326 may be preloaded to deform clamp 316 to tighten around externalspline 314, thereby eliminating backlash or “slop” between middle bellcrank 304 and torsion bar 302. Any method of preloading clamp 316 may beutilized, such as a separate clamp or a bolt. In the illustratedembodiment, securing tabs 324, 326 each include an aperture 328, 330through which a bolt 332 is insertable. A nut 334 threads onto bolt 332to tighten securing tabs 324, 326 against one another.

External spline 314 includes outward-facing teeth 336 and internalspline 318 includes inward-facing teeth 338. Inward-facing teeth 338 ofclamp 316 mate with outward-facing teeth 336 of torsion bar 302.Outward-facing teeth 336 are substantially parallel to one another andextend radially outward from torsion bar 302. Inward-facing teeth 338are substantially parallel to one another and extend radially inwardtoward the central longitudinal axis of torsion bar 302. Outward- andinward-facing teeth 336, 338 may have any shape that allows for amateable or interlocking fit. In the illustrated embodiment, each ofoutward- and inward-facing teeth 336, 338 are flat-topped teeth. Inother embodiments, the spline formed by clamp 316 and torsion bar 302may be a parallel key spline, involute spline, crowned spline, serratedspline, helical spline, ball spline, standard spline pattern or anyother type of spline.

In some embodiments, a shim (not shown) may be inserted between securingtabs 324, 326 to control tightening of clamp 316 onto torsion bar 302.Any size shim may be used. For example, if the application calls for atightness around torsion bar 302 such that gap 340 between securing tabs324, 326 is 20/1000ths of an inch, then a 20/1000ths of an inch shim maybe inserted into gap 340 to ensure proper tightening of clamp 316.Middle bell crank 304 may be formed from any material, such as steel,including stainless steel. While a clamped spline connection is shownwith reference to middle bell crank 304, the clamped splines disclosedherein may be used to connect other portions or parts of the enginemount assembly. For example, a clamp spline connection may be used toconnect the top and bottom end bell cranks to the ends of torsion bar302.

Middle bell crank 304 includes a bell crank arm 342 that bifurcates intotwo tines 344, 346. Tines 344, 346 each form an aperture 348, 350.Lateral link 308 has two ends 352, 354. Bolt 356 is inserted through end354 of lateral link 308 and apertures 348, 350 such that end 354 oflateral link 308 is rotatably coupled to, and interposed between, tines344, 346 of bell crank arm 342. End 352 of lateral link 308 bifurcatesinto tines 358, 360. Beam spring 306 is interposed between tines 358,360. Beam spring 306 and tines 358, 360 each form an aperture throughwhich bolt 362 is inserted to fixedly couple end 352 of lateral link 308to middle section 364 of beam spring 306. The connection between end 352of lateral link 308 and beam spring 306 is adjacent to midpoint 366 ofbeam spring 306, although, in other embodiments, the connection betweenend 352 of lateral link 308 and beam spring 306 may occur anywhere inmiddle section 364 of beam spring 306, including midpoint 366 itself.Middle bell crank 304 is coupled to beam spring 306 such that therotational energy of torsion bar 302, caused by lateral movement of theengine, is transferable to beam spring 306. In particular, middlesection 364 of beam spring 306 receives the rotational energy of torsionbar 302 when torsion bar 302 rotates. Each end 368, 370 of beam spring306 is coupled to support spine 372 to form two connections 374, 376with support spine 372.

Beam spring 306 has a lateral stiffness that resists rotation of middlebell crank 304. The lateral stiffness of beam spring 306 is exerted asmiddle bell crank 304, via lateral link 308, pulls or pushes againstmiddle section 364 of beam spring 306 while opposing ends 368, 370 arepinned, or otherwise coupled, to support spine 372. Beam spring 306resists rotation of torsion bar 302 during operation of the engine mountassembly such that lateral movement of the engine is controllable basedon the lateral stiffness of beam spring 306. The lateral stiffness ofbeam spring 306 may be determined by the geometry, shape or material ofbeam spring 306. In the illustrated embodiment, beam spring 306 is aflat beam, although beam spring 306 may have any shape, cross-section orprofile. Beam spring 306 may be formed from any material having anystiffness or elasticity, including steel or stainless steel. The shapeof beam spring 306 is such that beam spring 306 has necks 378, 380 thatare adjacent to ends 368, 370 and have reduced widths. Midpoint 366 ofbeam spring 306 has a greater width than necks 378, 380. The width ofbeam spring 306 gradually increases from necks 378, 380 to midpoint 366.

Connections 374, 376 at ends 368, 370 of beam spring 306 may be formedin a variety of ways. In the illustrated embodiment, each end 368, 370forms an aperture through which bolts 382, 384 are inserted to mountbeam spring 306 to support spine 372. While the illustrated embodimentshows beam spring 306 providing the lateral stiffness of lateralmovement control assembly 300, in other embodiments other components ordevices may provide a lateral stiffness, such as a coiled spring,flexure, elastomeric member or cantilevered beam. Beam spring 306 mayprovide spatial advantages compared to other types of springs since beamspring 306 has a slender profile that is easily mountable against othercomponents, such as support spine 372. Although beam spring 306 isillustrated to provide a lateral stiffness for the lateral movementcontrol assembly 300, a pinned beam spring may be used anywhere in theengine mount assembly to provide stiffness for any purpose.

Referring to FIGS. 14-16, 17A-17B and 18 in the drawings, an enginemount assembly utilizing one or more sleeved bolt assemblies isschematically illustrated and generally designated 400. In particular,FIG. 17A, which is a cross-sectional view taken along line 17A-17A ofFIG. 15, and FIG. 17B illustrate sleeved bolt assembly 402 beingutilized to secure blade 404 of bottom scissor mount 406 to engine lug408 of engine 410. It will be appreciated by one of ordinary skill inthe art, however, that sleeved bolt assembly 402 may be used anywhere onengine mount assembly 400 to secure any number or combination of partsto one another. For example, sleeved bolt assembly 402 may also be usedto secure blade 412 to engine lug 414 such that both blades 404, 412 ofbottom scissor mount 406 are each secured to engine 410 using arespective sleeved bolt assembly of the illustrative embodiments.Sleeved bolt assemblies may also be used to secure top scissor mount 416to engine 410.

Sleeved bolt assembly 402, as illustrated, secures blade 404 to enginelug 408. Engine lug 408 protrudes from bottom side of 418 of engine 410.Engine lug 408 forms aperture 420. Blade 404 bifurcates into tines 422,424 each forming an aperture 426, 428 that substantially aligns withaperture 420 of engine lug 408. Engine lug 408 is interposed betweentines 422, 424 of blade 404. A bolt 430, having a head 432 and a stem434, is inserted through aperture 426 of tine 422, aperture 420 ofengine lug 408 and aperture 428 of tine 424 to secure blade 404 toengine lug 408. Tines 422, 424 and bolt 430 approximate a clevisarrangement, although the use of sleeved bolt assembly 402 is notlimited to such arrangements. Bolt 430 is undersized relative to alignedapertures 420, 426, 428 to form a circumferential gap 436 around stem434 of bolt 430 and within apertures 420, 426, 428. A sleeve 438, whichis cylindrically shaped and has a central channel 440 therethrough, isinserted to partially, substantially or fully fill circumferential gap436. In the illustrated embodiment, sleeve 438 is disposed in all threealigned apertures 420, 426, 428. Central channel 440 of sleeve 438receives stem 434 of bolt 430.

Aligned apertures 420, 426, 428 have two entry ends 442, 444 into whicheither bolt 430 or sleeve 438 may be inserted. In the illustratedembodiment, bolt 430 is inserted at entry end 442 and sleeve 438 isinserted at entry end 444. In other embodiments, however, bolt 430 maybe inserted at entry end 444 and sleeve 438 may be inserted at entry end442. Such interchangeability of insertion may be useful when limitedclearance to surrounding structures does not permit the insertion ofeither bolt 430 or sleeve 438 through one of entry ends 442, 444. Asbest seen in FIG. 17B, which is a cross-sectional view taken along line17B-17B of FIG. 17A, sleeved bolt assembly 402, with the inclusion ofsleeve 438, allows bolt 430 to be undersized relative to apertures 420,426, 428. In this cross-section, aperture 426 has a diameter 446. Sleeve438 has a wall thickness 448. Stem 434 of bolt 430 has a diameter 450that is equal or approximate to D−(2T), wherein D is diameter 446 ofaperture 426 and T is wall thickness 448 of sleeve 438. At least one end452 of sleeve 438 may include a flange 454. Flange 454 may perform avariety of functions, including limiting the insertion of sleeve 438into circumferential gap 436 or acting as a washer against which a nut456 may be threaded. Sleeve 438 may be made from any material, includingsteel such as high temperature-tolerant steel. High temperature-tolerantsteel may be suitable when sleeved bolt assembly 402 is used at or nearhigh temperature components, such as engine 410.

As best seen in FIG. 17A, aperture 428 of tine 424 has a larger diameterthan both aperture 426 of tine 422 and aperture 420 of engine lug 408,thereby forming an outer circumferential gap 458 at entry end 444. Aslip bushing 460 is insertable into outer circumferential gap 458 suchthat flange 454 abuts slip bushing 460. Slip bushing 460 may be used topush engine lug 408 against tine 422 when sleeved bolt assembly 402 isfully engaged, thereby providing a tighter fit between these elements.End 462 of bolt 430, which is opposite of head 432, may include athreaded portion 464 onto which nut 456 may be threaded to abut flange454 of sleeve 438. Nut 456 is undersized to accommodate undersized bolt430, thereby increasing clearance 466 between sleeved bolt assembly 402and surrounding structure, such as engine 410. Sleeved bolt assembly 402may also include a washer 468, and threaded portion 464 of bolt 430 mayinclude a safety hole (not shown) adjacent to nut 456 into which a pin(not shown), such as a cotter pin, may be inserted to prevent parts ofsleeved bolt assembly 402 from disengaging.

Bolt 430, being undersized, permits increased clearance 466 between head432, nut 456 or other portions of sleeved bolt assembly 402 andstructure surrounding sleeved bolt assembly 402, such as engine 410.Such increased clearance 466 also allows increased access to installsleeved bolt assembly 402. For example, regular-sized bolts and nuts maybe too large to install due to obstruction by the structure and shape ofengine 410. FIG. 18 shows a traditional bolt stack up with a traditionalbushing arrangement. In FIG. 18, the bolt substantially fills apertures420, 426, 428. The traditional bolt assembly in FIG. 18 has a reducedclearance 470 with engine 410. The regular-sized bolt in FIG. 18 may beunable to be installed due to its large size, in particular because ofthe obstruction caused by engine 410. Thus, sleeved bolt assembly 402 ofthe illustrative embodiments is particularly well-suited to secureelements with tight clearances to adjacent structure. Despite having areduced size for bolt 430 and nut 456, sleeved bolt assembly 402maintains load or shear requirements due to the additional stresstolerance supplied by the added thickness 448 of sleeve 438. Thus,sleeved bolt assembly 402 increases clearance 466 to adjacent structurewhile maintaining strength requirements for use in high loadenvironments, such as engine mounts. It will be appreciated by one ofordinary skill in the art that although sleeved bolt assembly 402 isshown to secure scissor mount 406 to engine 410, sleeved bolt assembly402 may be used to secure any type of mount to engine 410. Furthermore,any number of sleeved bolt assemblies may be used in engine mountassembly 400.

The foregoing description of embodiments of the disclosure has beenpresented for purposes of illustration and description. It is notintended to be exhaustive or to limit the disclosure to the precise formdisclosed, and modifications and variations are possible in light of theabove teachings or may be acquired from practice of the disclosure. Theembodiments were chosen and described in order to explain the principalsof the disclosure and its practical application to enable one skilled inthe art to utilize the disclosure in various embodiments and withvarious modifications as are suited to the particular use contemplated.Other substitutions, modifications, changes and omissions may be made inthe design, operating conditions and arrangement of the embodimentswithout departing from the scope of the present disclosure. Suchmodifications and combinations of the illustrative embodiments as wellas other embodiments will be apparent to persons skilled in the art uponreference to the description. It is, therefore, intended that theappended claims encompass any such modifications or embodiments.

What is claimed is:
 1. An engine mount assembly for coupling an engineto an airframe, the engine mount assembly comprising: a torsion barcoupled between the engine and the airframe, the torsion bar having atleast one end including a tapered boss; at least one arm assemblycoupling the at least one end of the torsion bar to the engine, the atleast one arm assembly including an end bell crank having a taperedsocket; and a lateral movement control assembly coupled between thetorsion bar and the airframe, the torsion bar rotating in response tolateral movement of the engine; wherein the tapered socket of the endbell crank is adapted to receive the tapered boss on the at least oneend of the torsion bar to secure the end bell crank to the torsion barsuch that the end bell crank rotates with the torsion bar responsive tomovements of the engine.
 2. The engine mount assembly as recited inclaim 1 wherein the tapered boss further comprises a plurality oftapered sides forming a substantially polygonal boss; and wherein thetapered socket further comprises a plurality of tapered sides forming asubstantially polygonal socket.
 3. The engine mount assembly as recitedin claim 1 wherein the tapered boss further comprises first, second andthird tapered sides forming a substantially triangular boss; and whereinthe tapered socket further comprises first, second and third taperedsides forming a substantially triangular socket.
 4. The engine mountassembly as recited in claim 1 wherein the tapered boss furthercomprises a plurality of tapered sides each having the same taper angle;and wherein the tapered socket further comprises a plurality of taperedsides each having the same taper angle.
 5. The engine mount assembly asrecited in claim 4 wherein the plurality of tapered sides of the taperedboss have substantially the same taper angle as the plurality of taperedsides of the tapered socket.
 6. The engine mount assembly as recited inclaim 1 wherein the tapered boss further comprises a plurality oftapered sides; wherein the tapered socket further comprises a pluralityof tapered sides; and wherein each of the plurality of tapered sides ofthe tapered boss is adapted to abut one of the tapered sides of thetapered socket.
 7. The engine mount assembly as recited in claim 1further comprising: a fastener; wherein the tapered boss furthercomprises a receiving hole; wherein the tapered socket further comprisesan aperture; and wherein the fastener is insertable into the apertureand the receiving hole to tighten the tapered socket against the taperedboss.
 8. The engine mount assembly as recited in claim 7 wherein thereceiving hole further comprises a threaded receiving hole; and whereinthe fastener further comprises a screw threadable into the receivinghole.
 9. The engine mount assembly as recited in claim 1 wherein the endbell crank further comprises a bell crank arm having a distal endforming a bell crank arm socket.
 10. The engine mount assembly asrecited in claim 9 wherein the at least one arm assembly furthercomprises a linkage having first and second ends; wherein the bell crankarm socket is adapted to receive the first end of the linkage; andwherein a bolt is insertable through at least one linkage securingaperture and the first end of the linkage to secure the first end of thelinkage within the bell crank arm socket.
 11. The engine mount assemblyas recited in claim 1 wherein the engine is subject to torsionalmovement and wherein the end bell crank rotates in response to torsionalmovement of the engine.
 12. The engine mount assembly as recited inclaim 1 wherein the at least one arm assembly further comprises: ascissor mount attachable to the engine; and a linkage coupling thescissor mount to the end bell crank.
 13. The engine mount assembly asrecited in claim 1 wherein the lateral movement control assembly reactsto the rotation of the torsion bar such that lateral movement of theengine is controllable based on a lateral stiffness of the lateralmovement control assembly.
 14. The engine mount assembly as recited inclaim 1 wherein the lateral movement control assembly further comprises:a middle bell crank fixedly coupled to the torsion bar; and a springcoupled to the middle bell crank, the spring having the lateralstiffness to control lateral movement of the engine.
 15. A rotorcraftcomprising: an airframe; an engine; an engine mount assembly adapted tomount the engine to the airframe, the engine mount assembly including: atorsion bar having at least one end including a tapered boss; at leastone arm assembly coupling the at least one end of the torsion bar to theengine, the at least one arm assembly including an end bell crank havinga tapered socket; and a lateral movement control assembly coupledbetween the torsion bar and the airframe, the torsion bar rotating inresponse to lateral movement of the engine; wherein the tapered socketof the end bell crank is adapted to receive the tapered boss on the atleast one end of the torsion bar to secure the end bell crank to thetorsion bar such that the end bell crank rotates with the torsion barresponsive to movements of the engine.
 16. The rotorcraft as recited inclaim 15 wherein the tapered boss further comprises a plurality oftapered sides each having the same taper angle and forming asubstantially polygonal boss; wherein the tapered socket furthercomprises a plurality of tapered sides each having the same taper angleand forming a substantially polygonal socket; and wherein the pluralityof tapered sides of the tapered boss have substantially the same taperangle as the plurality of tapered sides of the tapered socket.
 17. Therotorcraft as recited in claim 15 wherein the tapered boss furthercomprises a plurality of tapered sides each having the same taper angleand forming a substantially polygonal boss; wherein the tapered socketfurther comprises a plurality of tapered sides each having the sametaper angle and forming a substantially polygonal socket; and whereineach of the plurality of tapered sides of the tapered boss is adapted toabut one of the tapered sides of the tapered socket.
 18. A tiltrotoraircraft having a helicopter mode and an airplane mode, the tiltrotoraircraft comprising: an airframe including a fuselage, a wing and anacelle; an engine disposed within the nacelle; an engine mount assemblyadapted to mount the engine to the airframe, the engine mount assemblyincluding: a torsion bar having at least one end including a taperedboss; at least one arm assembly coupling the at least one end of thetorsion bar to the engine, the at least one arm assembly including anend bell crank having a tapered socket; and a lateral movement controlassembly coupled between the torsion bar and the airframe, the torsionbar rotating in response to lateral movement of the engine; wherein thetapered socket of the end bell crank is adapted to receive the taperedboss on the at least one end of the torsion bar to secure the end bellcrank to the torsion bar such that the end bell crank rotates with thetorsion bar responsive to movements of the engine.
 19. The tiltrotoraircraft as recited in claim 18 wherein the tapered boss furthercomprises a plurality of tapered sides each having the same taper angleand forming a substantially polygonal boss; wherein the tapered socketfurther comprises a plurality of tapered sides each having the sametaper angle and forming a substantially polygonal socket; and whereinthe plurality of tapered sides of the tapered boss have substantiallythe same taper angle as the plurality of tapered sides of the taperedsocket.
 20. The tiltrotor aircraft as recited in claim 18 wherein thetapered boss further comprises first, second and third tapered sidesforming a substantially triangular boss; and wherein the tapered socketfurther comprises first, second and third tapered sides forming asubstantially triangular socket.